Multiple altitude satellite relay system and method

• US 5,971,324 A
• Filed: 11/27/1996
• Issued: 10/26/1999
• Est. Priority Date: 10/03/1995
• Status: Expired due to Term

• Current Assignee: Northrop Grumman Systems Corporation (Northrop Grumman Corporation)
• Original Assignee: TRW Inc. (Northrop Grumman Corporation)
• Inventors: Williams, Brian R., Cress, Peter H.
• Primary Examiner(s): Mojica, Virna Lissi
• Application Number:
  US08/757,542
• Time in Patent Office: 1,063 Days
• Field of Search: 244/158 R, 342/356, 342/357, 701/13, 455/12.1, 455/13.1
• US Class Current: 244/158.4
• CPC Class Codes: B64G 1/1007 Communications satellites
• CPC Class Codes: B64G 1/1085 Swarms and constellations
• CPC Class Codes: B64G 1/242 Orbits and trajectories
• CPC Class Codes: H04B 7/195 Non-synchronous stations

Abstract

A multiple altitude satellite relay system is disclosed in which Medium Earth Orbit satellites are continuously linked with at least one geosynchronous satellite to provide uninterrupted relaying of messages and data. The Medium Earth Orbit satellites are synchronized with the geosynchronous satellites to produce continuous links. A parameter to achieve the synchronization involves the positions of the Medium Earth Orbit satellite relays relative to the positions of the geosynchronous satellite relays. Another parameter to achieve synchronization involves the ratio between the orbital periods of the geosynchronous satellite relays relative to the orbital periods of the Medium Earth Orbit satellite relays. These parameters may be further adjusted to provide continuous links above the horizon of the earth. An additional satellite relay system is disclosed in which the high-orbit satellite need not be in geosynchronous orbit and in which a high-orbit satellite communicates over a continuous unbroken link with a low-orbit satellite. A further satellite relay system is disclosed in which more than two satellites are arranged at discrete orbit altitudes, again providing a continuous, unbroken daisy-chain link between satellites.

Claims

1. A multiple altitude satellite system which is capable of maintaining continuous, unbroken links between satellites disposed at different altitudes, comprising:

a first satellite orbiting at one of a low and medium-earth-orbit altitude; and

at least one second satellite orbiting at a high orbit altitude, said high orbit being synchronized with the orbit of said first satellite to maintain a continuous line-of-sight between said first and second satellites.

2. The multiple altitude satellite system of claim 1 wherein an orbital period of said second satellite relative to an orbital period of said first satellite is at a predetermined ratio.

3. The multiple altitude satellite system of claim 2 wherein said predetermined ratio is a 3:

1 ratio.

4. The multiple altitude satellite system of claim 2 wherein said predetermined ratio is a 2:

1 ratio.

5. The multiple altitude satellite system of claim 4 wherein said line-of-sight is continuously above-the-horizon of the earth.

6. The multiple altitude satellite system of claim 2 wherein said line-of-sight is continuously above-the-horizon of the earth.

7. The multiple altitude satellite system of claim 1 wherein said line-of-sight is continuously above-the-horizon of the earth.

8. The multiple altitude satellite system of claim 1 wherein distance of said line-of-sight above the earth is based upon position of said second satellite relative to the position of said first satellite and upon inclination angle of orbit plane of said first satellite.

9. The multiple altitude satellite system of claim 8 wherein an orbital period of said second satellite relative to an orbital period of said first satellite is at a predetermined ratio.

10. The multiple altitude satellite system of claim 1 wherein said first satellite includes means for providing a link with said second satellite.

11. The multiple altitude satellite system of claim 10 wherein said link between said first satellite and said second satellite is a radio link.

12. The multiple altitude satellite system of claim 10 wherein said link between said second satellite and said first satellite is a laser-based link.

13. The multiple altitude satellite system of claim 1 wherein said first satellite includes means for providing a link with an earth-based user.

14. The multiple altitude satellite system of claim 1 wherein said first satellite includes means for providing a link with an earth-based control station.

15. The multiple altitude satellite system of claim 1 wherein said first satellite includes means for relaying communications.

16. The multiple altitude satellite system of claim 1 wherein said second satellite includes means for relaying communications.

17. The multiple altitude satellite system of claim 1 wherein said first satellite includes means for relaying data.

18. The multiple altitude satellite system of claim 1 wherein said second satellite includes means for relaying data.

19. A method of providing a multiple altitude satellite system which is capable of maintaining continuous, unbroken links between satellites disposed at different altitudes, comprising the steps of:

providing a first satellite at one of a low and medium-earth-orbit altitude and a second satellite at an altitude higher than that of said first satellite; and

synchronizing the orbit of said first satellite with an orbit of said second satellite to maintain a continuous line-of-sight between said first and second satellites.

20. The method of claim 19 further comprising the step of:

configuring said first satellite so that an orbital period of said second satellite relative to an orbital period of said first satellite is at a predetermined ratio.

21. The method of claim 20 further comprising the step of:

configuring said first satellite so that an orbital period of said second satellite relative to an orbital period of said first satellite is at a 3;

1 ratio.

22. The method of claim 20 further comprising the step of:

configuring said first satellite so that an orbital period of said second satellite relative to an orbital period of said first satellite is at a 2;

1 ratio.

23. The method of claim 22 further comprising the step of:

configuring said first satellite to have said line-of-sight to be continuously above-the-horizon of the earth.

24. The method of claim 20 further comprising the step of:

configuring said first satellite to have said line-of-sight to be continuously above-the-horizon of the earth.

25. The method of claim 19 further comprising the step of:

configuring said first satellite to have said line-of-sight to be continuously above-the-horizon of the earth.

26. The method of claim 19 further comprising the step of:

configuring said first satellite whereby distance of said line-of-sight above the earth is based upon position of said second satellite relative to the position of said first satellite and upon inclination angle of orbit plane of said first satellite.

27. The method of claim 26 further comprising the step of:

configuring said first satellite so that an orbital period of said second satellite relative to an orbital period of said first satellite is at a predetermined ratio.

28. The method of claim 19 further comprising the step of:

providing a link between said first satellite and said second satellite.

29. The method of claim 28 wherein said link between said first satellite and said second satellite is a radio link.

30. The method of claim 28 wherein said link between said first satellite and said second satellite is a laser-based link.

31. The method of claim 19 further comprising the step of:

providing a link between said first satellite and an earth-based user.

32. The method of claim 19 further comprising the step of:

providing a link between said second satellite and an earth-based control station.

33. The method of claim 19 further comprising the step of:

relaying communications between said first and second satellite.

34. The method of claim 19 further comprising the step of:

relaying data between said first and second satellite.

35. A multiple altitude satellite system for maintaining continuous unbroken links between satellites disposed at different altitudes, comprising:

a first satellite orbiting in one of a medium-earth-orbit altitude and a low-earth-orbit altitude; and

at least one second satellite orbiting at an altitude higher than said first satellite, said second satellite being synchronized with the orbit of said first satellite to maintain a continuous line-of-sight between said first and second satellites.

36. The multiple altitude satellite system of claim 35, wherein an orbit period of said low-earth-orbit/medium-earth satellite relative to an orbital period of said high earth orbit satellite is at a predetermined ratio.

37. The multiple altitude satellite system of claim 35 wherein said predetermined ratio is 2:

1.

38. The multiple altitude satellite system of claim 35 wherein said predetermined ratio is 3:

1.

39. The multiple altitude satellite system of claim 35 wherein said line-of-sight is continuously above-the-horizon of the earth.

40. The multiple altitude satellite system of claim 35 wherein said satellites include means for providing a link therebetween.

41. The multiple altitude satellite system of claim 40 wherein said link between said first satellite and said second satellite is a radio link.

42. The multiple altitude satellite system of claim 40 wherein said link between said second satellite and said third satellite is a laser-based link.

43. The multiple altitude satellite system of claim 35 wherein at least one of said first and second satellites include means for providing a link with an earth-based user.

44. The multiple altitude satellite system of claim 35 wherein at least one of said first and second satellites include means for providing a link with an earth-based control station.

45. The multiple altitude satellite system of claim 35 wherein said first satellite includes means for relaying communications.

46. The multiple altitude satellite system of claim 35 wherein said second satellite includes means for relaying communications.

47. A multiple altitude satellite system for maintaining continuous, unbroken links between satellites disposed at different altitudes, comprising:

a first satellite orbiting at a high-earth-orbit altitude;

a second satellite orbiting at an intermediate-earth-orbit altitude; and

a third satellite orbiting at a low-earth-orbit altitude, said first, second, and third satellites being synchronized in orbit with respect to one another to maintain continuous lines of sight therebetween.

48. The multiple altitude satellite system of claim 47, wherein orbit periods of said first, second, and third satellites are at a predetermined ratio to one another.

49. The multiple altitude satellite system of claim 48, wherein said predetermined ratio is 4:

2;

1.

50. The multiple altitude satellite system of claim 48, wherein said predetermined ratio is 6:

3;

1.

51. The multiple altitude satellite system of claim 47 wherein said lines-of-sight are continuously above-the-horizon of the earth.

52. The multiple altitude satellite system of claim 47, wherein said first, second, and third satellites include means for providing a link therebetween.

53. The multiple altitude satellite system of claim 52 wherein said link between said first satellite and said second satellite is a radio link.

54. The multiple altitude satellite system of claim 52 wherein said link with said first satellite is a laser-based link.

55. The multiple altitude satellite system of claim 47 wherein one of said first, second, and third satellites includes means for providing a link with an earth-based user.

56. The multiple altitude satellite system of claim 47 wherein one of said first, second, and third satellites includes means for providing a link with an earth-based control station.

57. The multiple altitude satellite system of claim 47 wherein one of said first, second, and third satellites includes means for relaying communications.

58. The multiple altitude satellite system of claim 47 wherein said second satellite includes means for relaying communications.